The present invention relates to torque transmitting fluid couplings, and more particularly, to such couplings which utilize temperature-responsive bimetal coils to control the operation of the valving which, in turn, controls the flow of fluid within the coupling, and the torque transmission thereof.
Fluid couplings of the type to which the present invention relates are well known in the art and may be better understood by reference to U.S. Pat. Nos. 3,055,473; 3,174,600; and 3,339,689, assigned to the assignee of the present invention. Briefly, such couplings typically include an output member and a cover which cooperates to define a fluid chamber, a valve plate dividing the fluid chamber into an operating chamber and a reservoir chamber, and an input member disposed within the operating chamber and rotatable relative to the output member. A valving arrangement controls the flow of fluid between the operating and reservoir chambers, typically, in response to ambient air temperature external to the fluid coupling. Therefore, it is common to mount the valve member on a valve shaft which projects outwardly to the cover and has one end of a bimetal coil connected thereto, with the other end of the bimetal coil fixed relative to the cover. Changes in ambient air temperature cause the bimetal coil to unwind or wind tighter, thus rotating the valve shaft.
In the type of fluid coupling described above, it is normally necessary to provide some form of support for the valve shaft, permitting it to rotate relative to the cover. Among the well known and commercially used arrangements for supporting the valve shaft is that shown in U.S. Pat. Nos. 3,263,783 and 3,559,786, wherein a portion of the stamped cover is formed into a cylindrical flange, and, more recently, that shown in copending application Ser. No. 692,106, filed June 3, 1976 (assigned to the assignee of the present invention), wherein a separate cylindrical support insert is seated within a central circular opening in the cover. In either case, the shaft support portion normally projects to extends outwardly beyond the surface of the cover member a substantial distance, e.g., at least about 1/8 to 3/16 of an inch. As may be seen in the cited patents, it has been accepted practice to position the bimetal coil outwardly from the valve support portion (i.e., further away from the cover member), thus defining an area between the bimetal coil and the cover member which is essentially wasted space.
As the trend toward compact and subcompact automobiles has developed, it has become necessary to reduce the size of many of the engine accessory components, especially the axial dimensions thereof. This has also been true in the case of fluid coupling devices to which the present invention relates, and which are typically used in automotive applications as the drive for the radiator cooling fan.